There are 26 credited producers on the Broadway production of Terrence McNally's theater-biz satire It's Only a Play, and presumably nobody will be laughing harder than those guys at the zingers about the phalanx of moneymen who now regularly mob the Radio City stage when winners are announced on Tony Awards night. The in-jokes come thick and fast in this extensively retooled revival, which has been raking in huge grosses through previews thanks to its deluxe cast.

The big draw is the reteaming of Nathan Lane and Matthew Broderick, the adored double-act who made the Mel Brooks musical The Producers a commercial juggernaut and demonstrated their box-office clout again in a 2005 revival of Neil Simon's The Odd Couple. But it's in Lane's dynamite early scenes with gifted newcomer Micah Stock that this funny if flimsy comedy really fires on all cylinders, while Broderick underwhelms in a key role.

McNally's farcical doodle starts out like gangbusters but becomes increasingly uneven. It has an annoying habit of stalling when it should accelerate, particularly in a padded second act that could use an editor. Still, there's much enjoyment to be had from this amusing sketch, first performed in 1978 and then overhauled in 1982. That version has been revised in subsequent productions to update its many insider references to the current Broadway landscape.

Basically, it's a two-hour-40-minute New Yorker cartoon set in the Manhattan townhouse of a dilettante producer as she and her guests await the opening-night reviews of a new play. A razor-toothed parody of that most insular showbiz species, Broadway theater folk, it's also an affectionate valentine to them.

What keeps it entertaining even when the writing falters is McNally's equal-opportunity ribbing of everyone involved — playwrights, producers, actors, directors, theater landlords, stagehands, etc. That favorite punching bag, the critic, takes a beating; even doddery matinee audiences with their faulty listening devices ("What did she say?") get an irreverent jab. Just the sheer volume of jokes being fired off ensures that anyone even vaguely familiar with Broadway lore will be laughing.

Director Jack O'Brien presides over the well-upholstered production, on a set by Scott Pask that bespeaks an occupant with more wealth than taste. The action takes place in the creamy boudoir of Julia Budder (Megan Mullally), a clueless neophyte who has stepped out from the investor herd to be lead producer on The Golden Egg, a new work by eternally promising American dramatist Peter Austin (Broderick).

As the party rolls on downstairs and celebrity guests come and go (yielding a number of choice coat gags, the best of them making merry with Tommy Tune, Daniel Radcliffe and Lady Gaga), various key personages wander in and out of the room. The most constant presence is James Wicker (Lane), a talented character actor who abandoned the stage for a network TV series that just wrapped its ninth season. But its future is in doubt; cue nervous calls to his agent on the West Coast. Having turned down the male lead that his old friend Peter wrote for him, James has flown in for the opening, rubbing his hands with bitchy glee when the play turns out to be a dud.

Also on hand to wait out the seemingly inevitable death knell of the New York Times review with a modicum of self-deluding optimism is lead actress Virginia Noyes (Stockard Channing). That pill-popping, coke-snorting Hollywood refugee is looking for career rehab with a return to the stage following an unfortunate scandal. Then there's the wunderkind Brit director du jour, Frank Finger (Rupert Grint), a kleptomaniac glam-rock dandy who claims to crave the unfamiliar sting of failure. There's also an acerbic critic with an agenda, Ira "The Eviscerator" Drew (F. Murray Abraham), and Gus (Stock), the starry-eyed coat-check boy, fresh off the bus and eager to be discovered.

McNally stuffs every scene with digs at Broadway and its denizens — James Franco's sexting, Alec Baldwin's hot temper, Shia LaBeouf's erratic behavior, Harvey Fierstein's masculinity — a large proportion of which are pretty darn hilarious. There's also a cheeky streak of self-referential humor in nods to the playwright's own work, and in particular, to Lane and his past roles. "But what do I know?" asks James at one point. "I liked The Addams Family." And Grint's character briefly sports what might almost be a Cloak of Invisibility swiped from Hogwarts.

But ultimately, this starts to feel less like the tight collaboration of a writer and director intent on keeping the comedy machinery humming than the product of an overcrowded writers' room full of gagmeisters trying to outdo one another. There's sweet poignancy as well as cruelty in McNally's depiction of self-regarding creative types slowly and painfully absorbing the body blows of a flop. Their despair is actually quite touching, and when their defenses are down, an unwitting suggestion of genuineness creeps into their insincerity. But the second act devolves into sloppy plotting and diminishing returns as the play wheezes across the finish line.

It's Only a Play begs to be done as a brisk one-act. Instead, McNally places a cliffhanger intermission just as the Times review is about to be read. That pause lets some of the buoyancy escape the comedy. Even before that, however, Broderick's droning monologues have taken their toll. Most of those are shoehorned in to make belabored points — about the near-extinction of original American writing on Broadway; the British monopoly; the transformation of the theater district into a mall; the rise of the commercial bottom-feeder, "the Kardashians in Three Sisters" being a cautionary example.

While Broderick is an appealing performer, he's doing what's become his familiar shtick. By pitching Peter somewhere between Buster Keaton and Stan Laurel, with a naive-sounding, singsong delivery out of a Frank Capra movie, he undermines how much the anxious playwright has at stake with this opening night. The actor's droll monotone yields arguably the show's single-most uproarious laugh, when Peter responds to Ira's facetious question, "What wouldn't you do for a good review?" But Broderick seems to be performing a routine, not playing an actual character.

O'Brien doesn’t quite get all the actors on the same page. Abraham comes on full of arrogant bluster but gets steadily sidelined, even before Ira does. Grint appears to have wandered in from an Ab Fab episode, doing an exaggerated brand of British TV comedy that doesn't always jibe with that of his castmates. Mullally is daffy and charming, making the most of Julia's oblivious misquotes, though her vocal performance seems calibrated for a smaller space.

Channing is divine. She makes Virginia martini-dry but also a touch blowsy, suggesting she hasn't yet surrendered her vanity but she can glimpse its retreat. Stock is a real find, his lisping Gus an eager-to-please rube among sophisticates, with a subtle hint of Eve Harrington. However, it's Lane who does the heavy lifting, with his mastery of the delayed double take, the arched eyebrow, the wry aside and the incredulous repetition of each outrageous slight against James, a backstabber with a core of vulnerability.

With box office north of $1.2 million a week and hefty advance sales, It's Only a Play, unlike The Golden Egg, probably doesn't need reviews. Either way, while the vehicle is not exactly robust, McNally and O'Brien know the terrain well enough to ensure that it sparkles more often than it sags.